The invention relates to an image processing method for noise reduction in a sequence of noisy images representing a threadlike structure on a background.
The invention particularly relates to a noise reduction method applied to a sequence of medical X-ray fluoroscopy images representing a catheter guide-wire. The invention also relates to a system for carrying out this method and to an examination apparatus having means for image processing.
The invention is applied to the medical examination apparatus industry.
An image processing system for filtering X-ray fluoroscopic image sequences is already known from U.S. Pat. No. 5,809,105. This document discloses means for acquiring an image by passing X-rays through a subject, said image comprising an array of pixel values, means for receiving the image and producing a mask therefrom, which distinguishes the pixel values that correspond to structural features in the image, from the pixel values that correspond to background and means being responsive to the mask for selectively filtering the pixel values in the image that corresponds to background. So, the mask is used to select the background pixels for filtering the background noise while enabling the structural pixels to pass to the display unfiltered. The means for filtering the background pixel values include a Poisson filter which is a spatial filter.
This known method does not provide enhancing means of the structure of interest which is always difficult to see in a fluoroscopic image when said structure is a threadlike structure such as a guide-wire. Besides, this known method does not take into account that structure may move very swiftly on the background and that the background may be difficult to filter without degradation of the structure for that reason.
It is an object of the invention to provide a method of enhancing the thread-like structure pixel values, to improve the background noise reduction without degradation of said thread-like structure.
This aim is attained by a method for noise reduction in a sequence of noisy original images representing a thread-like structure moving on a background. The method includes an acquisition of a pixel value at a current pixel location in a first and a second successive original image of the sequence, and comprising processing steps for producing a filtered pixel value at said current pixel location for reconstructing a filtered second image. The processing steps include a step of extraction of the threadlike structure for producing first and second binary mask image pixel values at said location from the first and second original image pixel values, steps of producing spatially and temporally filtered pixel values of the second original image, and a step of pixel value selection based on the binary mask image pixel values for producing respectively, as a finally filtered pixel value, either the temporally filtered pixel value as a background filtered pixel value, or the spatially filtered pixel value as a threadlike-structure filtered pixel value.
This aim is attained by a method for noise reduction in a sequence of noisy original images representing a thread-like structure moving on a background. The method includes an acquisition of a pixel value at a current pixel location in a first and a second successive original image of the sequence, and comprising processing steps for producing a filtered pixel value at said current pixel location for reconstructing a filtered second image. The processing steps include a step of extraction of the threadlike structure for producing first and second binary mask image pixel values at said location from the first and second original image pixel values, steps of producing spatially and temporally filtered pixel values of the second original image, and a step of pixel value selection based on the binary mask image pixel values for producing respectively, as a finally filtered pixel value, either the temporally filtered pixel value as a background filtered pixel value, or the spatially filtered pixel value as a threadlike-structure filtered pixel value [as claimed in claim 1].
A system for carrying out the above-described method is also included, as well as an examination apparatus with a system and means for carrying out the processing method described.